<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    /*h1{color: red}*/
    /*h1{color: #ff0000}*/
    /*h1{color: #f00}*/
    /*h1{color: rgb(255,0,0)}*/
    h1{color: rgba(255,0,0,0.5)}
  </style>
</head>
<body>
<h1>颜色测试</h1>
</body>
</html>